Method and apparatus for dynamically allocating harq processes in the uplink

ABSTRACT

Methods and apparatus for dynamically allocating HARQ processes are described. A wireless transmit/receive unit (WTRU) includes a receive unit configured to receive signaling and a transmit unit. The transmit unit is configured to transmit uplink data sequentially using a first integer number of hybrid automatic repeat request (HARQ) processes during normal HARQ operation and transmit uplink data using a second integer number of HARQ processes that is less than the first number of HARQ processes in response to receiving the signaling.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/841,156 filed Aug. 20, 2007, which claims the benefit of U.S.Provisional Application No. 60/839,172, filed Aug. 21, 2006, U.S.Provisional Application No. 60/829,457, filed Oct. 13, 2006, U.S.Provisional Application No. 60/863,543, filed Oct. 30, 2006, and U.S.Provisional Application No. 60/868,185, filed Dec. 1, 2006, the contentsof which are hereby incorporated by reference herein.

FIELD OF INVENTION

The present invention is related to a wireless communication systems.More particularly, a method and apparatus for dynamically allocatinghybrid automatic repeat request (HARQ) processes for wirelesstransmit/receive units (WTRUs) in the uplink is disclosed.

BACKGROUND

The uplink capacity in a code division multiple access (CDMA)-basedsystem, such as high speed packet access (HSPA), or a single channelfrequency division multiple access (SC-FDMA) system, such as an evolveduniversal terrestrial radio access network (E-UTRAN), is limited byinterference. For a CDMA-based system, uplink interference at a specificcell site is typically generated by WTRUs, (i.e., users) connected tothe cell as well as WTRUs connected to other cells. In the case of anSC-FDMA-based system, uplink interference stems primarily from WTRUsconnected to other cells. To maintain coverage and system stability, acell site can tolerate only up to a certain amount of uplinkinterference at any given instant in time. As a result, system capacityis maximized if interference can be kept constant as a function of time.This consistency allows a maximum of users to transmit and/or generateinterference without having the uplink interference exceeding apredetermined threshold at any time.

High-speed uplink packet access (HSUPA), as defined in the ThirdGeneration Partnership Project (3GPP) Release 6, employs HARQ withsynchronous retransmissions. When utilizing a 2 millisecond (ms)transmission timing interval (TTI), the minimum instantaneous data rateis often larger than the data rate offered by an application, due to theneed to transmit a number of bits that is at least the size of a singleradio link control (RLC) protocol data unit (PDU) in a given TTI. Whenthis occurs, a WTRU can utilize only a subset of the available HARQprocesses. As a result, the interference generated by a given activeWTRU is not constant over a time span of eight (8) TTIs. During someTTIs, the WTRU transmits data and the interference it generates is high.During other TTIs, the WTRU may only transmit control information and,therefore, the interference it generates is low. In order to equalizeinterference across all TTIs, the system can restrict each WTRU to use acertain WTRU-specific subset of HARQ processes, and select differentsubsets for different WTRUs.

Transmissions from a WTRU for a certain stream of data may be managed bynon-scheduled transmissions or scheduling grants. With non-scheduledtransmissions, the WTRU can freely transmit up to a fixed data rate incertain HARQ processes. With scheduling grants, the WTRU can alsotransmit up to a certain data rate on certain HARQ processes, but themaximum data rate is subject to change dynamically depending on themaximum power ratio signaled by a Node-B at a given time.

When the network manages the transmission by allowing non-scheduledtransmissions, the set of HARQ processes is signaled to the WTRU throughradio resource control (RRC) signaling. The Node-B determines the set ofHARQ processes and signals this information to the radio networkcontroller (RNC), which then relays it to the user through RRCsignaling. An advantage of managing delay-sensitive traffic withnon-scheduled transmissions is that it eliminates the possibility of anyadditional delay that could be caused by insufficiency of the resourcesgranted by the Node-B when managing the transmissions with schedulinggrants. Another advantage is that it eliminates the signaling overheaddue to the transmission of scheduling information that is required withscheduling grants.

With the currently defined mechanisms for non-scheduled transmissions,however, the performance of the system is sub-optimal when theapplication mix is dominated by delay-sensitive applications thatgenerate traffic patterns exhibiting periods of high activity alternatedwith periods of low activity. An example of this type of application isthe voice over Internet protocol (VoIP) application, in which silenceperiods translate into a very low amount of traffic needing to betransmitted. When the cell or system is dominated by this type ofapplication, capacity is maximized only if the network is capable ofmodifying the subset of HARQ processes used by a WTRU when its activitystate changes, so that the interference is always equalized across theHARQ processes. Otherwise, the network has to restrict the number ofWTRUs utilizing a certain HARQ process so that the threshold is notexceeded, even when they are all active at the same time, resulting in amuch lower capacity.

An issue when utilizing non-scheduled transmissions is that it allowsmodification of the subset of allowed HARQ processes only through RRCsignaling, which typically involves latencies of several hundreds ofmilliseconds. This latency is significant compared to a typical intervalbetween changes of activity for applications such as voice applications.Furthermore, RRC signaling in the current Release 6 architecture iscontrolled by the RNC. Therefore, the Node-B needs to signal themodification of the subset of allowed HARQ processes to the RNCbeforehand. The interval of time between the change of activity state atthe WTRU and the effective change of HARQ processes may well be largerthan the duration of the activity state. Accordingly, this becomesunworkable for equalizing interference across HARQ processes.

It would therefore be beneficial to provide a method and apparatus fordynamically allocating HARQ processes in the uplink that would aid inoptimizing capacity with non-scheduled transmissions.

SUMMARY

Methods and apparatus for dynamically allocating HARQ processes aredescribed. A wireless transmit/receive unit (WTRU) includes a receiveunit configured to receive signaling and a transmit unit. The transmitunit is configured to transmit uplink data sequentially using a firstinteger number of hybrid automatic repeat request (HARQ) processesduring normal HARQ operation and transmit uplink data using a secondinteger number of HARQ processes that is less than the first number ofHARQ processes in response to receiving the signaling.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding of the invention may be had from thefollowing description of a preferred embodiment, given by way of exampleand to be understood in conjunction with the accompanying drawingswherein:

FIG. 1 shows an exemplary wireless communication system including aplurality of WTRUs, and a Node-B;

FIG. 2 is a functional block diagram of a WTRU and the Node-B of FIG. 1;

FIG. 3A is a flow diagram of a method of allocating processes;

FIG. 3B is a flow diagram of an exemplary implementation of the methodof FIG. 3A;

FIG. 4 is a flow diagram of a method of allocating processes, inaccordance with an alternative embodiment;

FIG. 5 is an exemplary diagram of system resource unit (SRU) allocationin accordance with the method of FIG. 4;

FIG. 6 is a flow diagram of a method of allocating processes, inaccordance with an alternative embodiment; and

FIG. 7 is a flow diagram of a method of allocating processes, inaccordance with an alternative embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of user device capable of operating in a wireless environment. Whenreferred to hereafter, the terminology “base station” includes but isnot limited to a Node-B, a site controller, an access point (AP), or anyother type of interfacing device capable of operating in a wirelessenvironment.

FIG. 1 shows an exemplary wireless communication system 100 including aplurality of WTRUs 110, a Node-B (NB) 120, and a radio networkcontroller (RNC) 130. As shown in FIG. 1, the WTRUs 110 are in wirelesscommunication with the NB 120, which is connected to the RNC 130.Although three WTRUs 110, one NB 120, and one RNC 130 are shown in FIG.1, it should be noted that any combination of wireless and wired devicesmay be included in the wireless communication system 100.

FIG. 2 is a functional block diagram 200 of a WTRU 110 and the NB 120 ofthe wireless communication system 100 of FIG. 1. As shown in FIG. 2, theWTRU 110 is in communication with the NB 120 and both are configured toperform a method of dynamic process allocation.

In addition to the components that may be found in a typical WTRU, theWTRU 110 includes a processor 115, a receiver 116, a transmitter 117,and an antenna 118. The processor 115 is configured to perform a dynamicprocess allocation procedure. The receiver 116 and the transmitter 117are in communication with the processor 115. The antenna 118 is incommunication with both the receiver 116 and the transmitter 117 tofacilitate the transmission and reception of wireless data.

In addition to the components that may be found in a typical NB, the NB120 includes a processor 125, a receiver 126, a transmitter 127, and anantenna 128. The processor 115 is configured to perform a dynamicprocess allocation procedure. The receiver 126 and the transmitter 127are in communication with the processor 125. The antenna 128 is incommunication with both the receiver 126 and the transmitter 127 tofacilitate the transmission and reception of wireless data.

FIG. 3A is a flow diagram of a method 300 of allocating processes. Ingeneral, the method 300 involves signaling to the WTRU 110 a subset ofallowed HARQ processes. This signaling is preferably used for thoseWTRUs 110 utilizing non-scheduled transmissions with 2 ms TTIs, andthose enabled to utilize the method 300. Also, preferably, theinformation required for enablement is communicated to the networkthrough RRC signaling that is defined over one or more TTIs.

In step 310, HARQ processes to be activated or deactivated areidentified and signaled to a WTRU 110 or group of WTRUs 110 (step 320).This signaling may be performed in a variety of ways.

For example, in one preferred method, each time a signal command issent, an individual HARQ process is either activated or deactivated,depending on its current activation state. In this way, the number ofbits that require encoding depends on the maximum number of HARQprocesses. For eight (8) HARQ processes, as are used in HSUPA, 3 bitswould need to be signaled, plus an additional bit that indicates whetherthe HARQ process is to be activated/deactivated. It could also beimplicit that the command signal toggles between activation anddeactivation, where the last bit would be omitted since it would beunneeded. However, in this manner, the WTRU 110 would have to knowbeforehand how to interpret the signal.

Another alternative method could be that each time the command signal issent, one HARQ process is activated and another HARQ process isdeactivated. In this method, enough bits to encode two HARQ processes,(e.g., six (6) bits), would be required. In this manner, a HARQ processthat is deactivated may be activated and a HARQ process that isactivated may be deactivated. Alternatively, all active HARQ processesmay be deactivated, and all deactivated HARQ processes may be activated.

Steps 310 and 320 of method 300 may also be performed by implicitlysignaling the activation or de-activation of an individual HARQ processby the transmission time of the signaling, such as the frame andsub-frame. For example, a rule may be pre-established between theframe/sub-frame number of the signaling command and the HARQ processinvolved. In this way, no bit is necessarily required to specify anindividual HARQ process, but the NB 120 would be constrained toactivate/de-active the individual HARQ process only at a specific frameor sub-frame. However, a single bit may be utilized if desirable tosignal whether a process is activated or deactivated. Alternatively, acombination of methods may be used, such as by indicating de-activationof an individual process by the transmission time and indicating theactivation of a process by using a bit or bits, or vice versa.

Yet another alternative for employing steps 310 and 320 of the method300 of FIG. 3A is to utilize the signaling command to specify theactivation or deactivation of all HARQ processes at once. This may beaccomplished by defining a bit map where each bit represents a HARQprocess and the value of the bit indicates whether or not the processshould be activated or deactivated, or the active/deactive state of theprocess merely switched.

It should be noted that in the current state of the art, HARQ processnumerators, also referred to as HARQ process indices, are WTRU specific.However, the RNC 130 may align the numerators so that broadcastinformation may be used by all WTRUs 110 in communication with the RNC130. Alternatively, a particular WTRU 110 may be signaled before thecorrespondence between each bit of the bitmap and each HARQ processnumerator.

For example, there are eight (8) possible HARQ processes for each WTRUthat are identified with an index, (e.g., from 1 to 8). As the WTRUs 110are not synchronized with one another, HARQ process N for a particularWTRU 110 is generally not transmitted at the same time as HARQ process Nfor another WTRU 110. However, the NB 120 may desire to activate ordeactivate HARQ processes for multiple WTRUs 110 that are transmitted ata specific time. To enable this signaling to take place in a “broadcast”scenario, the HARQ process indices of the different WTRUs 110 should besynchronized so that HARQ process N for one particular WTRU 110 istransmitted at the same time as HARQ process N for any other WTRU 110.Alternatively, each WTRU 110 may be made aware in advance which processindex should be turned on or off if the NB 120 signals that allprocesses being transmitted at a given time, that may be specified bysome common reference, should be turned on or off.

In another way of performing steps 310 and 320 of the method 300 of FIG.3A, the WTRU 110 may be permitted to utilize an individual process thathas been “toggled off” under conditions pre-specified or signaled fromthe network beforehand. One of these conditions may include the bufferoccupancy of data for uplink transmission by the WTRU 110. The number ofbits associated with each individual process could vary and may indicatea priority of usage in that different priorities would correspond torespective different sets of conditions for usage of each individualprocess.

The number of bits may be equal to the maximum number of HARQ processes.For example, eight (8) bits are used for HSUPA. Alternatively, therequired number of bits could be reduced if the set of HARQ processesthat can potentially be activated for a particular WTRU 110 is smallerthan the maximum number of possible HARQ processes. The set ofpotentially activated HARQ processes could be signaled to the WTRU 110through higher-layers, (e.g., RRC) in the same way that a set ofrestricted HARQ processes is signaled.

The signaling command may also specify the set of allowed HARQprocesses, (i.e., those HARQ processes that the WTRU 110 can use foruplink transmission), taking effect immediately or at a fixed delay fromwhen the information is received by the WTRU 110. Alternatively, theupdated set of allowed processes can take effect at a time specified inthe signaling message itself. Preferably, the set of allowed HARQprocesses is signaled as an index into a table where multiple sets ofallowed HARQ processes are already pre-defined and known at the WTRU110. The number of bits representing the index will limit the number ofsets that can be pre-defined. The mapping between the index and set ofallowed HARQ processes can be pre-configured through higher layersignaling or the set of allowed HARQ processes can be explicitlysignaled to the WTRU 110 by enumerating the specific allowed processnumbers.

Another way to perform steps 310 and 320 of the method 300 of FIG. 3A isfor the signaling to specify the probabilities for which the WTRU 110should turn on or off individual HARQ processes. Preferably, a singleprobability value is signaled per HARQ process, (e.g., turn off), and asecond probability value, (e.g., turn on), is calculated by using thesignaled value according to a predefined rule. Alternatively, both theoff and on probabilities may be explicitly signaled to the WTRU 110.

For any of the above described methods, the signaling commands may besent (step 320), or directed, to an individual WTRU 110 or to aplurality of WTRUs 110.

In one preferred embodiment, the functionality of the enhanced dedicatedchannel (E-DCH) absolute grant channel (E-AGCH) may be extended bydefining additional interpretation of the information bits. The correctinterpretation may be known to the WTRU 110 by time multiplexing indifferent TTIs and/or by using different spreading codes. The times andcodes may be signaled to the WTRU 110 by the network. Additionally, theinterpretation may be implied by an identification code embedded in theE-AGCH such as the WTRU ID. This is equivalent to defining a newphysical channel with a new name, (e.g., enhanced active processindicator channel (E-APICH), that may be time and/or code-multiplexedwith the E-AGCH.

Currently, the E-AGCH identifies WTRUs 110 by masking the cyclicredundancy code (CRC) with enhanced radio network temporary identifiers(E-RNTIs) of 16 bits. This approach could be extended by definingadditional E-RNTIs for non-scheduled transmissions for the WTRUs 110that use both scheduled and non-scheduled transmissions. The WTRU 110should respond to more than one E-RNTI. It is also possible to separatescheduled and non-scheduled operations in time. For processes that havebeen allowed use by the RNC 130 for non-scheduled operation, the AGCHutilizes the bit interpretation as described in the embodiments above,while in other processes it utilizes the bit interpretation as utilizedin the current state of the art.

Additionally, the network may define groups of WTRUs 110 and E-RNTIvalues for these groups. This allows faster signaling in case some HARQprocesses need to be deactivated for multiple WTRUs 110. Accordingly, aparticular WTRU 110 can be associated with a set of E-RNTI values, amongwhich some may be common to multiple WTRUs 110. Further processing maybe similar to what is currently defined for the E-AGCH, such asconvolutional encoding followed by rate matching. There are additionalpossibilities in terms of coding rate, amount of rate matching, size ofCRC, and the like, to fit the required number of information bits on theE-AGCH or E-APICH. Preferably, the coding rate and rate matching shouldbe kept the same as the prior art E-AGCH to simplify decoding operationat the WTRU 110. By way of example, the E-AGCH may contain the WTRU IDinformation (E-RNTI)/CRC (16 bits) and 6 bits of payload. Depending onhow many bits are needed to encode the instructions, one or more E-AGCHtransmissions may be combined by concatenating their available bits. Inanother example, the E-RNTI/CRC field may be reduced from 16 bits to asmaller number of bits to increase the available number of bits.

Another way of signaling the WTRU 110 in step 320 may be to extend theE-RGCH/E-HICH functionality, or multiplex a newly defined channel withthese channels by utilizing distinct orthogonal sequences to contain thenew signaling. This option allows the transmission of a binary valueevery TTI. One or more WTRUs 110 is identified by an orthogonal sequence(signature). It is also possible to transmit three (3) binary values bynot combining the sequences in each of the three (3) slots of the TTI.However, this way may require greater transmission power. If the numberof orthogonal sequences required to support the new signaling and theexisting enhanced relative grant channel (E-RGCH)/enhanced HARQindicator channel (E-HICH) is insufficient, a different spreading codemay be utilized to contain the new signaling, allowing the reuse of theorthogonal sequences of the E-RGCH/E-HICH.

Alternatively, the format of the high speed shared control channel(HS-SCCH) may be modified to include activation/de-activation commands.The format for the additional bits may be similar to the methods setforth above for the E-AGCH.

In addition to the signaling methods for step 320 described above,various other techniques may be utilized. For example, the existingbroadcast control channel (BCCH)/broadcast channel (BCH) may be extendedto include the signaling information related theactivation/de-activation of individual HARQ processes. The existing RRCcontrol signaling may be extended to convey information related to theactivation/de-activation of individual HARQ processes. The high speedmedium access control (MAC-hs) header may be modified to includeactivation/de-activation commands, with the format for the additionalbits potentially being similar to one of the options described above forthe E-AGCH. For this particular example, as retransmissions areasynchronous in the downlink (DL), and since the WTRU 110 can typicallyonly decode the information once the downlink PDU decoding issuccessful, signaling options where an individual HARQ process isimplicitly indicated by the signaling time should preferably refer tothe transmission time of the HS-SCCH that corresponds to the firsttransmission for this downlink PDU.

To make the signaling compatible with the use of discontinuous reception(DRX) or discontinuous transmission (DTX) at the WTRU 110, it may berequired to impose rules to force the WTRU 110 to listen, (i.e., not bein DRX), during TTIs where it would otherwise be in DRX, when certainconditions are met.

For example, the WTRU 110 could be required to not utilize DRX for acertain period of time immediately following resuming or interruption ofvoice activity, so that the NB 120 may modify the activated HARQprocesses if needed. Alternatively, it could be required that the WTRU110 listens periodically during certain TTIs when it would otherwise bein DRX, according to a pre-determined pattern. By way of anotherexample, a WTRU 110 could be required to stop DRX, (i.e., listen in allTTIs), when the NB 120 deactivates a HARQ process until another HARQprocess is activated. Thus, the NB 120 that desires to modify the HARQprocess allocation of a particular WTRU 110 would start by de-activatingone of the HARQ processes knowing that the WTRU 110 will be listeningfor the activation of the new HARQ process. The converse rule, (activatefirst and deactivate second), is also possible. More generally, a rulecould be established that allows the WTRU 110 to activate DRX only whenit has a specified number of HARQ processes activated.

To ensure that the new set of HARQ processes corresponds to the DRX/DTXpattern the WTRU 110 is using, the network may signal DRX activateand/or DTX activate from the NB 120 to the WTRU 110. Alternatively,signaling could be done by higher layers. Since individual or group WTRUsignaling to enable or disable a process exists in the current state ofthe art, it can be extended to indicate conditions for usage of multipleprocesses.

The embodiments may also support macrodiversity. For example, aparticular WTRU 110 may be in a state where it transmits to one or moreNBs 120 (additional NBs not shown) in an active set in addition to itsserving NB 120, which then sends the data to the RLC to bemacro-combined. If the serving NB 120 changes the allocated HARQprocesses, the other cells in the active set may blindly detect uplinktransmissions from the WTRU 110 in the new HARQ processes, or theserving NB 120 may signal changes to the RNC 130 which then relates themto other NBs 120 in the active set.

Due to power control, all WTRUs 110 may be considered interchangeablewith respect to their contribution to uplink interference. The NB 120,therefore, has the ability to choose which WTRU 110 it transfers betweenprocesses. Accordingly, the NB 120 can choose not to change the HARQprocess allocation of WTRUs 110 in handover.

As WTRUs 110 move within the system, changes of E-DCH serving NB 120will be required periodically. In order to support this mobility,several alternatives exist for the behavior of the WTRU 110 and NB 120during this period. In one example, the WTRU 110 is allowed to transmiton any HARQ process that is not restricted by higher layers, (i.e., allprocesses are active), until it receives activation/de-activationcommands from the new serving NB 120. Alternatively, the WTRU 110 may bedisallowed to transmit on any HARQ process, (i.e., all processes areinactive), until it receives activation commands from the new serving NB120.

In another preferred embodiment, however, the WTRU 110 maintains thesame active/inactive state of each of its HARQ processes upon change ofE-DCH serving NB 120. The new E-DCH serving NB 120 then sends anactivation/de-activation command that changes the state of each HARQprocess. If the new serving NB 120 sends a de-activation command for aHARQ process that was already inactive, or an activation command for aHARQ process that was already active, the WTRU 110 may ignore thecommand. Optionally, the new serving NB 120 may signal theactive/inactive state of HARQ processes of the WTRU 110 by the RNC 130upon setup of the radio link through Iub. Such signaling would requirethat the old serving NB 120 signals this information to the RNC 130,again through Iub, prior to or upon the change of E-DCH (enhanced datachannel handler) serving Node-B.

The WTRU 110 then reacts to signaling that it receives (step 330). Thisreaction may include several variations. In one example, the WTRU 110may listen at least when the MAC-e state changes from no uplink data touplink data. A change from no data to data is indicated when N1 TTIshave elapsed where new data has arrived in the buffer. A change fromdata to no data is indicated when N2 TTIs have elapsed without new dataarriving in buffer. N1 and N2 may be signaled beforehand by the networkto the WTRU 110. If signaled specifically the WTRU 110 must then enableor disable the processes as instructed.

In an alternative example, if the WTRU 110 is signaled as a part of agroup of WTRUs, the WTRU 110 may decide randomly whether to execute theinstruction utilizing a probability that may be signaled by the network.In order to support synchronous retransmissions within a HARQ process,preferably the WTRU 110 should only be allowed to switch to a differentHARQ process once the current HARQ process is complete, that is, once apositive ACK has been received or the maximum number of retransmissionshas been met. Alternatively, if signaled as part of a group, the WTRU110 may wait a random amount of time before executing the instruction,where the random amount of time may be signaled to the WTRU 110beforehand by the network.

When DRX or DTX is activated, and if the WTRU 110 was previouslyinstructed to behave so by higher layer signaling, the WTRU 110 adjuststhe reference for its DRX and DTX pattern to correspond to the time ofthe last DRX or DTX activation signal, respectively. Alternatively theWTRU 110 adjusts the DRX/DTX pattern to correspond to the set of HARQprocesses signaled. The mapping of HARQ processes to DRX/DTX patternscould be pre-determined, or could be signaled ahead of time by higherlayer signaling.

In the current 3GPP Release 6 architecture, the RRC layer is terminatedat the RNC 130. When leaving control of the HARQ process activation tothe NB 120, the NB 120 may require information about the quality ofservice (QoS) requirements of the WTRU 110 to avoid an excessivereduction in the number of activated processes. Such a reduction of thenumber of activated processes in a non-scheduled operation wouldundesirably force the WTRU 110 to increase its instantaneous data rateduring its active processes and reduce the area over which it can meetits QoS. Accordingly, it may be useful to have the RNC 130 communicateinformation to the NB 120 regarding the WTRUs 110, or have the NB 120acquire the information in some other way.

For example, the RNC 130 may estimate the minimum number of HARQprocesses that need to be activated at a given time to support the WTRU110 transmissions. The RNC 130 has the capability of performing thisestimation since it knows what the guaranteed bit rate is and hascontrol over the throughput of the HARQ process through outer-loop powercontrol and HARQ profile management. The RNC 130 communicates thisnumber of HARQ processes to the NB 120 through NBAP signaling. The NB120 ensures that the WTRU 110 has at least this number of HARQ processesactivated at any time. Because of the simplicity, this process may bedesirable for the NB 120.

Additionally, the RNC 130 may provide the guaranteed bit rate to the NB120 through NBAP signaling. Based on the guaranteed bit rate, the NB 120estimates how many active HARQ processes are required at a given timeand activates individual processes accordingly. The NB 120 may alsodetermine to deactivate certain processes during periods of inactivity.

Alternatively, the RNC 130 may not provide any information to the NB120. Instead, the NB 120 may endeavor to maintain the number of activeHARQ processes for a given WTRU 110 to the smallest possible value withthe constraint that it never has to transmit more than one RLC PDU at atime unless all HARQ processes are already activated. The NB 120 coulddetect the transmission of more than one RLC PDU by inspecting thecontent of successfully decoded MAC-e PDUs. This approach providessignificant flexibility to the NB 120, but may be more complex toimplement.

Any HARQ process allocation changes and resulting DRX/DTX pattern orreference changes determined by NB 120 may be signaled to the RNC 130,which may signal those changes to a target NB 120 in case of handover.

In the current state of the art, the set of HARQ processes that the WTRU110 is allowed to use is indicated by the RNC 130 through L3 signaling.This signaling could be maintained, indicating the allowed HARQprocesses for the WTRU 110, which may be activated or deactivated by theNB 120 as per the various schemes described above. In addition, the RNC130 could indicate to the WTRU 110 the initial set of HARQ processes tobe activated.

FIG. 3B is a flow diagram of an exemplary implementation 305 of themethod 300 of FIG. 3A. In particular, the implementation 305 allows theRNC 130, NB 120 and WTRU 110 to optimize capacity, such as for VoIP orany other delay sensitive application. Upon call setup initiation (step370), a particular WTRU 110 is preferably provided with a list ofpotentially activated HARQ processes (step 375). Alternatively, if alist is not provided, the WTRU 110 may assume that it can potentiallyuse all HARQ processes. The RNC 130 also provides information to the NB120, preferably through NBAP to aid the NB 120 in determining therequired number of HARQ processes.

After the WTRU 110 commences transmission, the NB 120 beginsde-activating HARQ processes for which the interference in the system isthe greatest (step 380). Additionally, the NB 120 maintains as activethe HARQ processes for which interference was minimal.

The NB 120 then continuously monitors the activity of all admitted WTRUs110 in the system with non-scheduled transmissions (step 385) and triesto maintain the interference across all HARQ processes below aparticular threshold by changing the active HARQ processes as a functionof activity (step 390). There are numerous ways in which to perform step390.

One way is that when the NB 120 detects that a previously inactive WTRU110 becomes active, the NB 120 changes the set of active HARQ processesfor this WTRU 110 to HARQ processes where the interference is the least.Alternatively, if a previously active WTRU 110 becomes inactive, it canswap its set of active HARQ processes with the set of another activeWTRU 110. Additionally, the NB 120 could also deactivate most HARQprocesses of a particular WTRU 110 that has become inactive, andactivate other HARQ processes, such as where interference is minimal,when activity resumes.

Another alternative is that the NB 120 may monitor the interference oneach HARQ process and periodically re-allocate one of the HARQ processesof one WTRU 110 from the most interfered HARQ process to the leastinterfered HARQ process, provided that the maximum level of interferenceover all processes does not increase. That is, a most interfered withHARQ process in the WTRU 110 is deactivated and a least interfered withHARQ process in the WTRU 110 is activated.

FIG. 4 is a flow diagram of a method 400 of allocating processes, inaccordance with an alternative embodiment. Since the purpose of theE-APICH is to maintain an uplink interference profile that is as uniformas possible between HARQ processes, a group-wise allocation of systemresources is possible to the WTRUs 110.

In step 410 of the method 400 of FIG. 4, a system resource unit (SRU) isdefined. Preferably, the SRU is defined to be a combination of a HARQprocess and a granular amount of an interfering system resource, such asrate or power. The interfering system resource is preferably defined byconsidering that in an interference limited system, such as a CDMAuplink, there is only a finite amount of power or rate that can beutilized by transmitters simultaneously. Usage of more resources than isavailable will cause interference and likely loss of packets. Althoughin a preferred embodiment, the interfering system resource is typicallymeasured using rate or power, other measures can be used. Additionally,required signal-to-interference ratio (SIR), received power, uplinkload, (i.e., a fraction of UL pole capacity) are measures that may alsobe utilized.

In step 420 of the method 400 of FIG. 4, the SRUs are allocated to theWTRUs 110. In fact, all allocation in the present alternative embodimentof the invention is done using SRUs. Preferably, a group of WTRUs 110 isselected and allocated the same non-scheduled SRUs. Depending on how theSRU is defined this can be performed in a variety ways. For example, ifSRU=(HARQ process, power), then HARQ processes can be allocated via RRCsignaling, where power is allocated via a mechanism such as the E-AGCH.All SRU processes within a group are assumed active, and therefore, allHARQ processes are active. Fast allocation is used only to allocate SRUswithin the group. Optional “banning” of SRUs in a group is possible tomake sure that no WTRU 110 in a group uses a particular HARQ process ata given time.

The allocation of SRUs to WTRU groups may be performed by allocatingSRUs to single groups such that if this is the only group transmitting,system resources are now exceeded and successful communication isassured. However, when multiple groups are present, the total number ofSRUs allocated in a cell may exceed the total number of available SRUs.

FIG. 5 is an exemplary diagram of system resource unit (SRU) allocationin accordance with the method 400 of FIG. 4. In the example shown inFIG. 5, it may be assumed that a system supports 8 HARQ processes andonly 3 SRUs can be supported simultaneously. No WTRU group is allocatedSRUs such that it can induce self-interference. However, a total oftwice as many SRUs as are available have been allocated, making itpossible that interference will occur if the WTRUs 110 all transmit atthe same time. As shown in FIG. 5, the SRUs are allocated to groups ofWTRUs 110 designated as Group 1, Group 2, Group 3, and Group 4. However,it should be noted that the depiction of four groups is exemplary, andany number of groups could be envisioned. By allocating one or severalSRUs to groups of WTRUs 110, fast allocation of SRUs is then signaled bythe NB 120, preferably using the E-APICH, where the NB 120 ensures thatno two WTRUs 110 in a particular group are allocated the same SRU.

There are several advantages and challenges to a group-wise approach asdescribed in method 400. By grouping the WTRUs 110, scheduling in the NB120 may be simplified. For example, HARQ allocations are semi-staticbetween groups and dynamic only within a group. On the other hand, agroup provides both sufficient freedom and sufficient response time tokeep the interference profile relatively stable.

Additionally, signaling overhead may be reduced since only a singleE-APICH per group is required. All WTRUs 110 in a group monitor the sameE-APICH. Moreover, there is no need for individual “power grant” to aWTRU 110. A particular WTRU 110 can always be granted more or less powerin a given HARQ process by providing it more SRUs or by removing some.

However, as WTRUs 110 enter and leave the cell, a group may need to beupdated, which may lead to an increase in signaling overhead. Thisproblem may be mitigated by not updating a full group every time a WTRU110 enters or leaves a group. Because a particular WTRU 110 only needsto know its own group and its ID within a group the group updateoverhead can be reduced.

For example, if a WTRU 110 leaves a cell, it group is maintained intact,but the NB 120 does not allocate any SRUs to that WTRU 110. Similarly,if a WTRU 110 enters a cell, it may be added to a group which has anopening, for example due to a WTRU in a group previously leaving a cell,or a new group may be created, with this WTRU 110 as the only member.Other WTRUs 110 may subsequently be added to the newly created group. Inany case, the NB 120 may occasionally have to reconfigure the groups.However, this will likely be a very infrequent event.

Depending on the scheduler of the NB 120, the rate required or servicessupported by the group size of the WTRUs 110 may vary. Therefore, thereare a variety of ways in which to form the groups.

For example, the total SRUs per group may be fixed. The number of WTRUs110 per group may be fixed. The total of a particular individualresource, (e.g., rate, power, HARQ processes) per group may be fixed. Agroup may be comprised of WTRUs 110 with similar receivercharacteristics, (e.g. Multi-in-Multi-out (MIMO) enabled, Type-xreceiver). A group may also be comprised of WTRUs 110 with similarchannel qualities.

Although multiplexing and signaling options for group-wise E-APICH aresimilar to those described above for the per-WTRU fast allocation, thesignaling options may need to be modified. Since all HARQ processes areassumed active for a group, the E-AGCH in a given TTI includes the groupindex of the WTRU 110 to which this process is allocated. A specialindex or non-existing WTRU index may be used to ban the HARQ process forall WTRUs 110 in a group.

Additionally, implicit signaling via timing of transmission may not bepractical for a group, although it may be used as an overlay for banningthe HARQ process. Also, instead of a bit field, a symbol, (i.e.,multi-bit), field is used, where each symbol indicates which WTRU 110 ispermitted a particular HARQ process and a special symbol or non-existingWTRU index may be used to ban the process. For example, each WTRU 110may be assigned a position of a bit field. A “0” may indicate that theWTRU assigned to this position cannot use the process while a “1” mayindicate that the WTRU can use the particular process. Additionally, oneof the positions of the bit field might be assigned to no specific WTRU110, and rather be used to indicate that the process either can orcannot be used by any, or all, of the WTRUs 110.

FIG. 6 is a flow diagram of a method 600 of allocating processes, inaccordance with an alternative embodiment. In the present alternativeembodiment, non-scheduled operation may be enhanced by sending minimaldownlink signaling that includes enough information to a WTRU 110 fordynamically changing HARQ processes within the constraints specified inthe downlink signaling. The current RRC signaling of HARQ allocation fornon-scheduled operation may be made such that the HARQ processes arerestricted and staggered for the WTRUs 110 so that there is a smoothWTRU load distribution across the HARQ processes. However, this does notsmooth out the voice activity variations which can cause highinterference during some HARQ processes.

The RRC signaling of restricted and staggered HARQ allocation may beutilized to enhance non-scheduled operation. In step 610 of method 600,the RNC 130 makes a HARQ allocation. Once that HARQ allocation is made,a known-controlled pattern/hopping allocation may be utilized (step620). This known-controlled pattern/hopping may be used to move theWTRUs 110 that are on top of the RNC 130 allocation in such a way thatthe load of WTRUs per HARQ process remains as before, but the voiceactivity is smoothed out across HARQ processes. Preferably, theknown-controlled pattern/hopping distributes and smooths the variationsof voice activity while not disturbing the WTRU load distributionbenefits achieved by restriction and staggering of HARQ processes.Additionally, it may be bounded below by a non-scheduled HARQ processallocation that is restricted and staggered.

The known-controlled pattern/hopping is sent to a particular WTRU 110(step 630) in a variety of ways. For example, it may be sent by RRCsignaling or other downlink signaling, such as by the new physicalchannel E-APICH signaling described above. The pattern may be signaledat call setup time or during a call/session on a semi-static basis whichmay be needed to fine tune previous allocations due to changes in thesystem such as in load-variations.

Additionally, the known-controlled pattern/hopping may take the form ofany pattern that generally preserves the load balance of the WTRUs 110across the HARQ processes, as provided by the RRC allocation ofnon-scheduled operation. For example, it may take the form of sequentialhopping of HARQ processes, from the initial RNC allocation, based on amultiple of TTI period that may be specified in RRC or other downlinksignaling. The sequential hopping is circular over the maximum number ofHARQ processes and the hopping direction is picked randomly, forexample, with a 0.5 probability.

Alternatively, the RRC may initially allocate a set of HARQ processes tothe WTRU 110 and the WTRU 110 may “hop” among them periodically withsome multiple of TTIs specified in the RRC or other downlink signaling.In another alternative, the WTRU 110 hopping may be randomized based ona pseudo-random pattern and the hopping period specified by RRC or otherdownlink signaling.

In yet another alternative, the WTRU 110 may randomly select a signalednumber of processes to be used in each cycle of 8 processes, forexample, or the WTRU 110 may randomly decide, each TTI, whether totransmit or not according to a probability that may be signaled to theWTRU 110 beforehand. In another alternative, the probability coulddepend on the WTRU uplink buffer occupancy that is defined by thenetwork and signaled beforehand.

FIG. 7 is a flow diagram of a method 700 of allocating processes, inaccordance with an alternative embodiment. In the method 700 describedin FIG. 7, HARQ processes uses for uplink (UL) transmissions arerandomly selected by particular WTRUs 110 during selectionopportunities. Thes selection opportunities occur every M TTIs, where Mis preferably a multiple of the total number of HARQ processes, (e.g.,8, 16). The WTRU should be pre-configured through higher layers toselect P HARQ processes on which it is allowed to transmit until thenext selection opportunity.

In step 710, the RAN assigns a selection opportunity to each HARQprocess. Preferably, the RAN provides a selection probability between 0and 1 for each of the allowed HARQ processes, where the sum of theprobabilities for all HARQ processes equals 1. This allows the RAN tofavor some processes over others, based on such factors as interferencegenerated from scheduled WTRUs 110 and intercell interference. Therandom distribution that is used to select the HARQ processes issignaled by the RAN to the WTRU 110 or WTRUs 110. The signaling of theseparameters may be achieved using any of the signaling mechanismsdescribed above. The parameters can be signaled individually to eachWTRU 110, to a group of WTRUs 110 or for all WTRUs 110 at once.Preferably, updates to the parameters may be made at the frequency atwhich WTRUs 110 select HARQ processes or at a slower frequency.

At every selection opportunity, the WTRU 110 should retrieve the latestset of parameters signaled from the RAN (step 720). The WTRU 110 thenselects a first HARQ process by randomly selecting a HARQ process amongpotential processes (step 730), taking into consideration the selectionprobability of each process.

If another process is required (step 740), then the WTRU 110 randomlyselects among the remaining processes (step 730), taking intoconsideration the selection probability of the remaining processes. Theprocess continues until the number of processes on which the WTRU isallowed to transmit until the next selection opportunity (P) have beenselected.

In order to support synchronous retransmissions within a HARQ process,preferably the WTRU 110 should only be allowed to select a differentHARQ process once the current HARQ process is complete, for example oncea positive ACK has been received or the maximum number ofretransmissions has been met.

Although the features and elements are described in the preferredembodiments in particular combinations, each feature or element can beused alone without the other features and elements of the preferredembodiments or in various combinations with or without other featuresand elements. The methods or flow charts provided may be implemented ina computer program, software, or firmware tangibly embodied in acomputer-readable storage medium for execution by a general purposecomputer or a processor. Examples of computer-readable storage mediumsinclude a read only memory (ROM), a random access memory (RAM), aregister, cache memory, semiconductor memory devices, magnetic mediasuch as internal hard disks and removable disks, magneto-optical media,and optical media such as CD-ROM disks, and digital versatile disks(DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) module.

What is claimed is:
 1. A wireless transmit/receive unit (WTRU)comprising: a receive unit configured to receive signaling; and atransmit unit configured to: transmit uplink data sequentially using afirst integer number of hybrid automatic repeat request (HARQ) processesduring normal HARQ operation, and transmit uplink data using a secondinteger number of HARQ processes that is less than the first number ofHARQ processes in response to receiving the signaling.
 2. The WTRU ofclaim 1, wherein the transmit unit is further configured to transmit theuplink data using the second integer number of HARQ processessequentially.
 3. The WTRU of claim 1, wherein the first integer numberof HARQ processes is
 8. 4. The WTRU of claim 1, wherein the receive unitis configured to receive the signaling from a wireless network.
 5. TheWTRU of claim 1, wherein the transmit unit is further configured totransmit the uplink data using one HARQ process in each of a pluralityof transmission time intervals (TTIs).
 6. A method for use in a wirelesstransmit/receive unit (WTRU) comprising: the WTRU receiving signaling;the WTRU transmitting uplink data sequentially using a first integernumber of hybrid automatic repeat request (HARQ) processes during normalHARQ operation; and the WTRU transmitting uplink data using a secondinteger number of HARQ processes that is less than the first number ofHARQ processes in response to receiving the signaling.
 7. The method ofclaim 6, further comprising the WTRU transmitting the uplink data usingthe second integer number of HARQ processes sequentially.
 8. The methodof claim 6, wherein the first integer number of HARQ processes is
 8. 9.The method of claim 6, further comprising the WTRU receiving thesignaling from a wireless network.
 10. The method of claim 6, furthercomprising the WTRU transmitting the uplink data using one HARQ processin each of a plurality of transmission time intervals (TTIs).
 11. A basestation comprising: a transmit unit configured to transmit signaling;and a receive unit configured to: receive uplink data sequentially usinga first integer number of hybrid automatic repeat request (HARQ)processes during normal HARQ operation, and receive uplink data using asecond integer number of HARQ processes that is less than the firstnumber of HARQ processes in response to the signaling.
 12. The basestation of claim 11, wherein the base station is a Node-B.
 13. The basestation of claim 11, wherein the receive unit is further configured toreceive the uplink data sequentially using the second integer number ofHARQ processes.
 14. The base station of claim 11, wherein the firstinteger number of HARQ processes is
 8. 15. The base station of claim 11,wherein the receive unit is further configured to receive the uplinkdata using one HARQ process in each of a plurality of transmission timeintervals (TTIs).
 16. A method for use in a base station, the methodcomprising: the base station transmitting signaling; the base stationreceiving uplink data sequentially using a first integer number ofhybrid automatic repeat request (HARQ) processes during normal HARQoperation; and the base station receiving uplink data using a secondinteger number of HARQ processes that is less than the first number ofHARQ processes in response to the signaling.
 17. The method of claim 16,wherein the base station is a Node-B.
 18. The method of claim 16,further comprising the base station receiving the uplink datasequentially using the second integer number of HARQ processes.
 19. Themethod of claim 16, wherein the first integer number of HARQ processesis
 8. 20. The method of claim 16, further comprising the base stationreceiving the uplink data using one HARQ process in each of a pluralityof transmission time intervals (TTIs).